High/Low Idle at start up

Hello all, well it seems I have my first real fix to do since I got my vx. Lately my idle seems to drop from the normal idle point to 3-400 and occasionally stalls out from low idle. This only happens when I first start the engine after its been sitting (probably cooling off) for awhile and then goes back to normal after i press the gas a couple times. I am thinking this is probably a sensor, anyone else got any tips before I do diving into the troubleshooting manuals?

thanks
Keith

Anytime throttle problems + cold engine are involved, I would check the Intake Manifold Gasket.